Defrosting of refrigerators



E. R. GILL, SR 2,162,709

DEFROSTING OF REFRIGERATORS June 20, 1939.

2 Sheets-Sheet 1 Original Filed May 7, 1930 5 45545555? mu y-as w ll lllllll aflr/ m3 A? -/05 /00 a; gy 3;93

9b ATTORNEY.

June 20, 1939. E R 3 5 DEFROSTING OF REFRIGERATORS Original Filed May 7, 1930 2 -S et 2 J6 and 62.

Patented June 20, 1939 UNITED STATES PATENT OFFICE to General Motors Corporation, a corporation of Delaware Claim;

This application is a division of my copending application Serial No. 450,451 flledMay 7, 1930, now matured into Patent No. 2,084,730, granted June 22, 1937.

My invention relates to refrigerating apparatus. and more particularly to mechanism for automatically initiating defrosting periods.

The principal object of the invention herein claimed is to predetermine the intervals at which defrosting takes place so that the defrosting will not occur at undesirable intervals.

Another object of the invention is to automatically restore the refrigerating system to normal operation as soon as the defrosting period is over. r

The invention will be clear from the following description taken in conjunction with the accompanying drawings showing a preferred form and variations thereof, and of which:

Fig. 1 shows a refrigerating machine of the compressor type having my invention applied thereto;

Fig. 2 shows one modification thereof; and

Fig. 3 shows another modification.

The system of refrigeration apparatus to which the invention is applied is well known and comprises an electric motor a for operating a compressor b for compressing a volatile refrigerant, for example, sulphur dioxide. A pipe c connects the highpressure side of the compressor with the condenser d where the refrigerant is liquefied. The liquid is forced through pipe e to the valve I for controlling escape of liquid to the low pressure cooling pipes or units a in the region which is to be refrigerated. Evaporation of the refrigerant takes place and the vapor is drawn through pipe h to the low pressure side of the compressor b to complete the cycle.

A pipe l2 connects pipe 71 with, the metal bellows ll of the switch k for closing and opening the power circuit of the electric motor a, thereby starting and stopping the motor and the compressor. The switch It may be of the general type shown in U. S. Patents 1,658,342 and 1,805,701.

Bellows l l moves in response to variations of suction line pressure in pipe h and causes movemerit of an am it. Springs 4i and 82 act against arm l5 to control and limit the movement thereof caused by movement of bellows ll. Adjustment nuts are provided to vary the tension of springs Suitable and known snap action mechanism is provided whereby switch contacts 26, 21 and 2! are closed or opened in accordance with high and low pressures respectively.

riginal application May 7, 1930, Serial No. Divided and this application July 30, 1935. No. 33,812

The parts hereinbefore mentioned operate briefly as'follows:

Assuming the switch to be in open circuit position, the compressor is not working and the pressure on the low pressure side of the system is rising. When the temperature of the region surrounding the cooling unit rises to approximately 28 F. the pressure of the refrigerant causes the bellows II to expand sufilciently to raise the arm I! to clom the switch, whereupon the electric motor is started and the compressor operated thereby. This produces refrigeration in known manner and when the refrigerated region attains a given low temperature the bellows ll contracts and opens switch It to stop the motor and compressor.

By varying the resistance of the arm I! to upward movement, the degree of temperature at which the switch closes the motor circuit can be either raised orlowered. 'This is ordinarily accomplished by adjustment springs as shown. The circuit closing temperature may be raised by increasing the resistance to compression of the spring 40. This-means provides for the closing of the circuit under ordinary runningconditions, as when the temperature is to be allowed to rise as high as 28' F. The lower limit or range of working temperature maybe varied by means of the adjustable coil spring 02. Inasmuch as this spring tends to move the switch arm upward, a movement of the adjusting nut downward increases the upward urge of the spring and makes it more difilcult for the bellows to pull the switch arm down to open the motor circuit. The compressor therefore operates to produce a lower pressure on the low pressure side of the system and a correspondingly lower temperature of the refrigerated region before the motor circuit can be opened.

In refrigerating systems, the evaporator is maintained below 32 F. and moisture deposits thereon from the air and freezes, forming a coating of frost which builds up and must be periodically removed. To the known refrigerating device, I have added a novel defrosting mechanism which operates a switch in series with switch It. The defrosting period is automatically initiated by a chronometric device at selected times (as for example, midnight of each day). Preferably the defrosting period is terminated by a condition of the structure affected by the defrosting mechanism.

, Referring to the mechanism shown in the lower part ofFig. 1, an electric motor control switch is shown which comprises a base ill having a standard I M upon which is mounted the auxiliary bellows II' which communicates with the low pressure side of the system by the auxiliary pipe I2. The free end of the bellows is provided with a rod I02 which is pivoted at I03 to the switch lever I04. This lever is pivoted at I05 to the base I and its limits of movement defined by stops I 06 and I01 carried by the upright I00. The outward movement of lever I 04 is opposed by a coil spring I09 which surrounds the threaded rod 0 and abuts against the standard I 0|, and the nut III threaded on said rod. The resistance offered by said spring may be varied by adjustment of the position of said nut. A similar spring II2 and nut II3 provide a similar adjustable resistance for opposing the inward movement of the lever I04. ',I'he rod H0 is pivoted to said lever at II 4.

At the extremity of the lever I04 is a pivotal stud I I5 having a bore which receives a slideable pin IIS. This pin is pivoted at II1 to the frame IIB of a mercoid switch I I8, which is in series with the usualmotor switch It as shown by leads 50and 5|. Coil spring IIS surrounds said pin H6 and is interposed between stud I I5 and shoulder 1' of pin H6. Switch H8 is pivoted on a screw or stud 9 carried by the upright member 808 and an extension arm I 20 is attached to and turns with the mercoid switch I I0 and has shoulders I20 and I20" for supporting it in the position shown in full lines and at a slightly lower position respectively. The arrangement of these parts is such that when arm I04 is in full line position, the switch H8 is likewise in full line position, but upon movement of arm I04 to dotted line position the switch "8' will be suddenly snapped by spring II 6' on passing the dead center into its dotted line position, unless such responsive movement of switch H8 is prevented, in

which case arm I04 can move back and forth without moving the switch 8' out of the full line position.

An escapement awl I22 is pivoted at I23 to the upright I08 and is normally held in full line position bytension spring 28. The upright and of pawl I22 is provided with a shoulder I22" and at its lower end with -a shoulder I23. A curved rod I25 is secured to the lower extremity of said pawl I22 and by the action of spring I24 is held against the surface of a cam or eccentric I26 mounted on arbor I21. The arbor I21 is driven by the gears I28, I29, I30 and I3I, forming part of a clockwork train of a time keeping device of any type, which may be, for example, an ordinary eight-day clock. The gearing may be such as to cause one revolution of the eccentric per each 24 hours, or any other desired interval of time.

The device operates as follows:

So long as the pawl I22 remains in full line position and arm I20 is supported by the catch I20" received on the shoulder I22, the switch II8' remains in full line position and the motor circuit is made through the mercoid switch 8'. During such times, the repetition of the normal cycle is controlled by the ordinary switch It in a normal way. Such movements as take place of arm I 04 during such time are without effect upon the closing of the motor circuit through the switch I I8, the provision of spring I I6 permitting such movement of arm I04 to take place without imparting movement-to switch II8.

When the timekeeping device has rotated the eccentric into the dotted line position this movement shifts the pawl I22 also to dotted line position so that the shoulder I22 of pawl I 22 releases the shoulder I20 of arm I20, whereupon in case lever I04 is in dotted line position, or if not, then upon the next movement of said lever to said position, the arm I20 falls a short distance until it is stopped by the shoulder I20" engaging catch I23 of pawl I22. Such slight turning movement, however, of arm I20 and switch 8' leaves the motor circuit still complete through the mercoid switch 8', and the-normal cycle of operation still in effect through the main switch k.

Upon turningmovement of the clockwork and.

cam member I26, catch I23 is moved back by spring I 24 until the shoulder I20" is released by said catch I23, whereupon, if lever I04 is in dotted line position, or if not, then upon the next movement of said lever to such position, the arm I20 and switch I I8 are released and turn through the snapping action of the connection I I5, I I6, H6" and III to the dotted line position in which the motor circuit is broken by the mercoid switch I 8'.

So long as the mercoid switch remains in such motor circuit breaking position the motor and compressor are at rest and the temperature of the refrigerated region permitted to rise irrespective of whether the motor circuit is completed or broken at the principal motor control switch. The

defrosting cycle so instituted continues until the temperature of the defrosted region rises to a point productive of a pressure of the vapor in the auxiliary bellows I I considerably higher than that required to close the circuit through the main switch is and which is suflicient to cause such auxiliary bellows II to move the switchlever I04 and switch H8 from dotted to full line position, whereupon the shoulder I20 of arm I20 becomes engaged with catch I22 of pawl I22 and the motor circuit is completed through the switch II8 by turning to such full line. position. The arm I20 will then be supported by pawl I22 until the cocentric I26 has made almost a complete revolution, whereupon the described operation will be repeated after an interval which may be practically any desired interval of time, the normal cycle of operation occurring in sequence in the regular way during such interval.

The device of Fig. 2 is similar to that of Fig. 1 in all respects except that instead of providing a timekeeping device or clock for causing rotation of the eccentric I26 a cycle counting device is used. This device comprises a ratchet wheel I40 mounted on the same arbor as the gear I29 and given a step-by-step movement bya pawl arm I which is pivoted at I42 to the switch arm I04. Each normal cycle of operation of the system causes the pawl I4I to advance the wheel I40 a distance of one or more teeth and to interpose (at least) one defrosting cycle for each revolution of the eccentric I26. If by reason of the slight curvature of the eccentric, the rod I25 hasnot at the end of the defrosting cycle moved the pawl I22 sufficiently to bring the shoulder I22 into position for supporting the arm I20, another defrosting cycle will ensue, and thereafter the series of normal cycles will occur until the eccentric again reaches the position for tripping the arm I20. Such repetition of defrosting cycles might also occur in the operation of the device of Fig. 1.

The device of Fig. 3 is similar in all respects to that of Fig. 2, except that the pawl I4I for advancing the ratchet I40 is replaced by a lever I50 pivotally supported at I5I and carrying at its free end a pawl I52 pivoted thereto at I53. A flat spring I54 is secured to the 'arm I50 by a ,aroa'ioo screw I" and normally holds it in the position shown. The lever I" is provided with an armature I" which is attracted by an electro-magnet iil whenever'the same is energized. The magnet is connected either in shunt or in series with the motor by which the compressor is driven and is energized every time the motor circuit is closed by the principal motor control switch, which is once for every normal cycle. Such energization causes the long arm of lever Ill to be pulled downward whereby the toothed wheel I is advanced the pitch of one tooth in a counter-clockwise direction. When the motor circuit is open the magnet is deenergized and the spring I" thereupon returns the lever arm ill to the position shown. The gear I19 operates an eccentric as in Figs. 1 and 2 for causing a defrosting cycle to be interposed in a series of normal cycles as described in connection with the device of Fig. 1.

It will be obvious that in the system the normal control switch may be operated by a temperature responsive thermostat instead of by pressure of the evaporator. Also it will be clear that the invention may be applied to the control of other forms of energy supply, such as the control of fiow of gas by controlling valves. Various other art.

I claim:

1. A refrigerating system including means to supply energy thereto, a first energy supply control member, a second energy supply control member, said members being arranged in series with respect to supply of energy, means responsive to variations in temperature below a given temperature to actuate said first energy supply control member, means to periodically actuate said second energy supply control member to restrain the energy supply, and means responsive to temperature above said given temperature to actuate said second energy supply control member to restore the supply of energy.

2. A refrigerating system including means to supply energy thereto, a first energy supply control member, a second energy supply control member, said members being arranged in series with respect to supply of energy, means responsive to variations in pressure below a given pressure to actuate said first energy supply control member, means to periodically actuate said second energy supply control member to restrain *the energy supply, and means responsive to pressure above said given pressure to actuate said second energy supply control member to restore the supply of energy.

3. A refrigerating system including means to supply energy thereto, a first energy supply control member, a second energy supply control member, said members being arranged in series with respect to supply of energy, spring-resisted means responsive to variations in temperature below a given temperature to actuate said first energy supply control member, spring-resisted means to periodicallyv actuate said second ener y supply control member to restrain the energy supply, means responsive to temperature above said given temperature to actuate said second energy supply control member to restore the supply of energy, and means for adjusting the 70 spring-resisted means.

4. A refrigerating system including means to supply energy thereto, a firstenergy supply control member, a second energy supply control member, said members being arranged in series with respect to supply of energy, spring-resisted changes will be apparent to those skilled in the means responsive to variations in pressure below a given pressure to actuate said first energy supply control member, spring-resisted means to periodically actuate saidsecond energy supply control member to restrain the energy supply, means responsive to pressure above said given pressure to actuate said second energy supply control member to restore the supply of energy. and means for adjusting the springresisted means.

.5. A refrigerating system including means to supply energy thereto, a first energy supply control member, a second energy supply control member, said members being arranged in series with respect to supply of energy, means respon- 'sive to variations in temperature below a given temperature to actuate said first energy supply controlmember, means movable step-by-step to periodically actuate said second energy supply control member to restrain the energy supply,

and means responsive to temperature abovesaid given temperature to actuate said second energy supply control member to restore the supply of energy.

6. A refrigerating system including means to supply energy thereto, a first energy supply control member, a second energy supply control member, said members being arranged in series with respect to supply of energy, means responsive to variations in temperature below a given pressure to actuate said first energy supply control member, means movable step-by-step to.

period cally actuate said second energy supply control member to restrain the energy supply, and means responsive to pressure above said iven pressure to .actuate said second energy.

supply control member to restore the supply of energy.

7. In a refrigerating system. a compressor for compressing a gas or vapor, means comprising an electric circuit for driving said compressor, means responsive to a normal upper limit of temperature of the refrigerated region for closing said circuit to drive the compressor, a time keeping device and means actuated by said time keeping device to allow the temperature of the refrigerated reg on to rise above said normal upper limit, said time keeping device actuated means including means responsive to a given high temperature of the refrigerated region to close the circuit. a

8. In a refrigerating system, a compressor for compressing a gas or vapor, mechanism comprising an electric circuit for driving said compressor, means responsive to a normal upper limit of temperature of the refrigerated region for closing said circuit to drive the compressor, an electromagnetic counting device actuated by movement of said means, and means actuated by said counting device for temporarily causing a defrosting operation.

9. Refrigerating apparatus including a cooling un t, means for circulating a refrigerant medium through the cooling unit, control means for normally starting and stopping the circulation of refrigerant medium at predetermined high and low temperatures to provide normal refrigeration cycles, means for providing defrosting cycles includ ng chronometric means controlling the circulation of refrigerant for initiating defrosting cycles, and temperature responsive means responsive to a temperature of the cooling unit above said predetermined high temperature for terminating said defrosting cycles.

10. Refrigerating apparatus including a cooling unit, means for circulating a refrigerant medium through the cooling unit, and control means for normally starting and stopping the circulation of refrigerant medium at predeterf mined high and low temperatures of the cooling unit, said control means being provided with chronometric means for periodically raising to a predetermined higher temperature the temperature at which the circulation is started.

11. Refrigerating apparatus including a. cooling unit, means for circulating a. refrigerant medium through the cooling unit, control means for normally starting and stopping the circulation of refrigerant medium at predetermined high and low temperatures of the cooling unit to provide refrigerating and idle cycles, and

means operated mechanically independently of the said control means but responsive to the cycling of the circulating means for periodically raising the temperature at which the circulation is started.

12. Refrigerating apparatus including a cool-- ing unit, means for circulating a refrigerant medium through the cooling unit, control means for normally starting and stopping the circulation of. refrigerant medium at predetermined high and low temperature limits of the cooling unit to provide refrigerating and idle cycles of the circulating means, and a cycle counting device powered mechanically independently of said control means but responsive to the cycling of energized by electric energy flowing under the control of the control means to the circulating means for periodically controlling the supply of electric energy to the circulating means according to a different temperature of the cooling unit.

14. Refrigerating apparatus including a liquefying means and an evaporating means, control means for normally starting and stopping the action of the liquefying means at predetermined high and low evaporator temperatures to provide normal refrigerating cycles, means for providing defrosting cycles including chronometric means for controlling the action of the liquefying means for initiating defrosting cycles, and temperature responsive means responsive to a temperature of the evaporating means above said predetermined high temperature for'terminating the defrosting cycles.

15. Refrigerating apparatus including a liquefying means and an evaporating means, control means for normally starting and stopping the action of the liquefying means at predetermined high and low evaporator temperatures to provide normal refrigerating cycles, said control means being provided with 'chronometric means for periodically raising to a predetermined higher temperature, the temperature at which the action of the liquefying means is started.

1Q. Refrigerating apparatus including a liquefying means and 'an evaporating means, control means for normally starting and stopping the action of the liquefying means at predetermined high and low evaporator temperatures to provide normal refrigerating and idle cycles, and means operated mechanically independently of the control means but responsive to the cycling of the liquefying means for periodically raising the temperature at which the action of the liquefying means is started.

7. A refrigerator including a cooling unit, oscillated means for controlling the flow of a refrigerant through said unit, and a chronometric device for frustrating said oscillated means for a period.

18. A refrigerator including a cooling unit, means normally controlling the circulation of a refrigerant through said unit, means for frustrating said normal control means for a period, and means for limiting the duration of the period.

19. A refrigerator including a cooling unit, means normally controlling the circulation of a refrigerant through said unit, means for frustrating the normal control means during a period, and means for temporarily frustrating the second mentioned means.

.20. A refrigerator including a cooling unit, means normally controlling the circulation of a refrigerant through said unit, time controlled means for rendering said normal control means ineifective during a defrosting period, and means tioned means.

21. A refrigerator including a cooling unit, means normally controlling the circulation .of' .a refrigerant through said unit, a device for limiting the operation of said normal control means for a period of time, means for delaying the operation of the limiting device, and means for restoring the control of said cooling unit to said normal control means at the'end of said period.

22. A refrigerator including a cooling unit, means normally controlling the circulation of a refrigerant through said unit, and means for limiting the operation of said normal control means for a period of time and for limiting the duration of the period of time.

23. Refrigerating apparatus including a cooling unit, means for circulating a refrigerant medium through the cooling unit, means for conducting electric energy to said circulating means, temperature responsive means for normally controlling the supply of electric energy to said circulating means, and a. ratcheting device powered mechanically independently of said temperature responsive means for stopping the supply of energy to said circulating means.

24. Refrigerating apparatus including a 0601-.

ing unit, means for circulating a refrigerant medium through the cooling unit, means for conducting electric energy to said circulating means, temperature responsive means for normally controlling the supply of electric energy to said circulating means, a ratcheting device powered mechanically independently 'of said temperature responsive means for stopping the supply of energy to said circulating means, and electrically operated means for operating said ratcheting device.

25. Refrigerating apparatus'including refrigerant liquefying means and refrigerant evaporating means, means for supplying energy to the liquefying means, temperature responsive means for controlling the'supply of energy to the liquefying means, and a ratcheting device powered mechanically independently of said temperature responsive means for changing the control of the supply of energy to the liquefying means.

26. Refrigerating apparatus including refrigerant liquefying means and refrigerant evaporating means, means for supplying energy to the liquefying means, temperature responsive means for controlling the supply of energy to the liquefying means, and a ratcheting device poweredmechanically independently of said temperature responsive means for interrupting the supply of energy to the liquefying means.v

27. Refrigerating apparatus including refrigerant liquefying means and refrigerant evaporating means, means for supplying energy to the liquefying means, temperature responsive means for controlling the supply of energy to the liquefying means, and a ratcheting device operated by a portion of the energy supplied by said supply means for changing the control of the liquefying means.

EDWIN R. GILL, SR. 

